Flocked fabrics

ABSTRACT

The disclosure described novel adhesive compositions having improved cold flex characteristics and solvent resistance. The adhesive composition comprises a combination of a particular type of water-insoluble, self-cross-linking acrylic polymer and an acid polymer. These adhesives are useful in the usual applications and, in particular, in preparing laminated fabrics and flocked pile fabric.

United States Patent Inventor Frank Endrenyi, Jr.

Spartanburg, S.C. Appl. No. 20,035 Filed Mar. 16, 1970 Patented Oct. 26,1971 Assignee Deering Milliken Research Corporation Spartanhurg, S.C.

FLOCKED FABRICS 5 Claims, No Drawings v US. Cl 161/64, 161/67,260/80.73, 260/898 Int. Cl ..B32b 27/04, B32b 27/14, C08f 29/56 Field ofSearch 260/898; 161/64, 67

Primary Examiner-William J. Van Balen Attorneys-Norman C. Armitage andH. William Petry ABSTRACT: The disclosure described novel adhesive compositions having improved cold flex characteristics and solventresistance. The adhesive composition comprises a combination ofaparticular type of water-insoluble, self-cross-linking acrylic polymerand an acid polymer. These adhesives are useful in the usualapplications and, in particular, in preparing laminated fabrics andflocked pile fabric.

lFLOCIIED FABRICS BACKGROUND OF THE INVENTION This invention relates toa novel adhesive composition having improved cold flex characteristicsand solvent resistance, and more particularly to an adhesive compositioncomprising a combination of a particular type of water-insoluble,selfcrosslinking acrylic polymer and an acid polymer. These adhesivesare particularly useful for preparing flocked pile fabrics.

In the production of flocked fabrics by the deposition of fibrousmaterials such as rayon or nylon fibers upon adhesive coated substrates,it has been found to be difficult to obtain flocked fabrics which retaintheir flexibility upon exposure to low temperature. It has beenparticularly difficult to obtain flocked fabrics having the desirablecold flex characteristics and also solvent resistance so that theflocked fabrics can be dry cleaned as well as machine washed.

There are a number of adhesives commercially available which possessadequate cold flex characteristics and machine washability. However, inaddition to these desirable properties, it is also important foradhesive compositions to deposit films which provide satisfactoryabrasion resistance and resistance to organic solvents used in drycleaning. For example, there are commercially available adhesives,particularly acrylic adhesives, which exhibit good cold flexcharacteristics, and these are characterized as those which depositair-dried films having a torsional modulus of 300 ltgJcm. attemperatures such as from-40 C. to -55 C. hereinafter referred to asT;,,,,". This measurementrelates to the stiffness or softness of a film.Another method of indicating the softness of film is by "GlassTransition Temperature" (G.T.T.). The G.T.T. is defined as thattemperature at which a sheet of polymer is transformed from a glasslikesolid state to a softened state. Above the glass transition temperature,the volume of the polymer sheet increases more rapidly with an increasein temperature. The point at which this volume increase begins may bereadily determined in a plot of volume versus temperature. These glasstransition temperatures may be determined by standard A.S.T.M. heatdeflection temperature measurements such as, for example, A.S.T.M.D648-45T, issued 1941, revised 1944, 1945. Films prepared from suchadhesive compositions, however, are not durable to dry cleaningsolvents.

Attempts to improve the durability of such adhesive compositions byintroducing cross-linking cites into the polymers or by the addition ofthe cross-linking catalysts result in a more durable film but with acorresponding reduction in the coldflex properties. Likewise, attemptsto introduce plasticiz ing compounds into the harder durable polymers toimprove the cold flex properties have been unsuccessful since theplasticizers are extracted from the films by the dry cleaning solvents.Thus, there continues to be a need for adhesive compositions exhibitinggood cold flex and abrasion resistance characteristics, machinewashability and dry cleanability.

SUMMARY OF THE INVENTION Novel adhesive compositions are provided bythis invention and comprise a mixture of a water-insoluble,self-cross-linking acrylic polymer, an air-dried film of which has atorsional modulus of 300 lag/cm. at a temperature of less than about 40C. and a hydrophilic acid polymer comprising a major amount of an acidester and minor amounts of an acrylic acid. Films prepared from suchadhesive compositions exhibit improved cold flex characteristics,solvent resistance, abrasion resistance and machine washability. Theseadhesive compositions are useful wherever adhesives having theseproperties are desired such as, for example, in the preparation offlocked pile fabrics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The adhesive composition ofthis invention is prepared from a mixture comprising from about 80 to 99parts of a water-insoluble, self-cross-Iinking acrylic polymer having aT or glass transition temperature of less than about -40 C. and

from about 1 to 20 parts of a hydrophilic acid polymer comprising amajor amount of an acid ester and minor amounts of an acrylic acid.These adhesive compositions are useful for preparing flocked pilefabric, said pile fabrics comprising a substrate, a layer of theabove-described adhesive composition on at least one side of saidsubstrate, and a plurality of fibers, each having one end portionembedded in the adhesive layer.

Any of the water-insoluble, sielf-cross-linlting acrylic polymers havinga T or glass transition temperature of less than about 40C. can beutilized in the preparation of the adhesives. Acrylic polymers of thisnature are commercially available with T or G.T.T. offrom 40 C. to 60 C.

The preferred self-cross-linlring acrylic polymers are those comprisinga mixture of acrylic esters, acrylonitrile and methylol .acrylamide. Theacrylic esters are those obtained from acrylic acid or methacrylic acidwith cyclohexanol or a!- cohols having from 2 to 18 carbon atoms.Examples of such esters include ethyl acrylate, isopropyl acrylate,butyl acrylate, methyl methacrylate, Z-ethylehexyl acrylate, etc.Acrylic monomers having dual functionality such as the methylolacrylamides are particularly useful as one component in the mixture.Examples of these acrylamides include: N-methylol acrylamides; Nmethylol methacrylamicle; N-methyl-N- methylol acrylamide; etc. Thepresence of the methylol acrylamide in the water insoluble acrylicpolymer provides the desirable self-cross-linlring properties to thepolymer thus enabling the application, deposition and curing of thepolymer on the substrate without the necessity for includingcross-linking or curing agents which might deleteriously affect thedesirable properties of the adhesive. Therefore, the acrylic polymer isdesigned to be self-cross-linlting by incorporating therein from about0.5 to 5 percent by weight of a methylol acrylamide, based on the weightof the other components of the polymer. Generally, from about 2 to 3percent of the methylol acrylamide is utilized.

The acrylonitrile is included in the acrylic polymer mixture to improvethe durability of the polymer to dry cleaning solvents. The acrylicpolymer portion of the adhesive composition of this invention,therefore, generally will comprise from about to 95 parts of an acrylicester, from 2 to 15 parts of acrylonitrile and from about 0.5 to 5 partsbased on the combined weight of the acrylic ester and acrylonitrile, ofa methylol acrylamide.

Examples of the water-insoluble, self-cross-linlting acryiic polymerswhich are preferred for use in this invention include polymersobtainedfrom mixtures comprising: parts of ethyl acrylate, 10 parts ofacrylonitrile and 3 parts based on the combined weight of the ester andacrylonitrile, of N-methylol 'acrylamide; and 90 parts of butylacrylate, 10 parts of acrylonitrile and 2 parts based on the combinedweight of the acrylate and acrylonitrile, of N-methylol acrylamide.These acrylic polymers generally are prepared utilizing emulsionpolymerization techniques. Emulsions of this type are commerciallyavailable from the Rohm and Haas Company under such trade designationsas Rhoplex l(l 4" which has a T of 47 C., and from National Starch and.Chemical Corporation under such trade designations as Nacrylic 25-4445"which has a glass transition temperature of-5 l C.

In addition to the acrylic polymer, the adhesive composition of thisinvention also contains a hydrophilic acid polymer comprising a majoramount of an acid ester and minor amounts of an acrylic acid. Theincorporation of these acid polymers into the adhesive compositions ofthe invention produces adhesive compositions having improved abrasionresistance and renders the adhesives more durable to organic solvents.Generally, from about I to 20 parts of the hydrophilic acid polymer isincorporated into the mixture containing from about 80 to 99 parts ofthe self-cross-linking acrylic polymer.

The ester which is present in the acid polymer includes esters of lowmolecular weight polymerizable organic acids, i.e., those havingreactive unsaturated groups therein. with cyclohexanol or alcoholshaving 2 to 18 carbon atoms. Examples of the polymerizable acid whichmay be present in the acid mixture in either the acid or ester form,include acrylic acid, methacrylic acid, itaconic acid, crotonic acid,maleic acid, fumaric acid, cinnamic acid, etc. Mixtures of esters andacids are contemplated as useful. In a preferred embodiment, thehydrophilic acid polymer comprises from about 60 to 95 parts of anacrylic ester and from about to 30 parts of an acrylic acid.

In some instances, it is desirable to incorporate a small amount ofamethylol acrylamide into the acid polymer to provide self-cross-linkingproperties to the polymer. In these instances, from about 0.5 to 5percent of the methylol acrylamide, based on the combined weight of theother components of the acid polymer is utilized. Any of the methylolacrylamides described previously as being components in the acrylicpolymer may be utilized in this acid polymer. Examples of some of theacid polymers that may be used in the preparation of the adhesivecompositions of the present invention are polymerization products ofmixtures of: ethyl acrylate and acrylic acid; ethyl acrylate, acrylicacid and acrylamide; butyl acrylate and acrylic acid; ethyl acrylate andmethacrylic acid; ethyl acrylate, acrylic acid and N-methylolacrylamide; ethyl acrylate, acrylic acid and hydroxy propylmethacrylate; ethyl acrylate, acrylic acid, ethoxyethyl acrylate and N-methylol acrylamide; ethyl acrylate, methacrylic acid, acrylic acid, andN-methylol acrylamide; ethyl acrylate, methacrylic acid, dibutyl maleateand N- methylol acrylamide.

These acid polymers generally are prepared utilizing emulsionpolymerization techniques, although it is possible to prepare solutionsof these polymers in organic solvents. Examples of such solvents includebenzene, tolulene, chloroform, trichloroethylene, methyl isobutylketone, etc.

As mentioned previously, the adhesive composition of the inventioncomprises from about 80 to 99 parts of the water-insoluble,self-cross-linking acrylic polymer and from about 1 to 20 parts of thehydrophilic acid polymer. In addition to the two above-describedpolymers, the adhesive composition also may contain a small amount, forexample, up to about 2 to 3 percent or more of a cross-linking catalyst.The presence of this small amount of catalyst expedites the curing ofthe adhesive without a serious negative effect of the desirableproperties on the adhesive. Examples of such catalysts include ammoniumchloride, citric acid, oxalic acid, zinc chloride, ammonium citrate,etc. The adhesive compositions also may contain varying amounts ofthickeners to increase the viscosity of the adhesive as the applicationtechnique may require. Examples of such thickeners include thewell-known thickeners such as gum, methylcelluloses such as theMethocels available from the Dow Chemical Co., and neutralizedpolyacrylates. The viscosity of the adhesive compositions is varieddepending upon the particular structure and porosity of the structure towhich the adhesive is applied. For most textile woven fabrics, adhesivecompositions having viscosities of between about 50,000 to 500,000centipoises have been found quite suitable for coating the fabrics.Compositions having viscosities of about 75,000 to 100,000 centipoisesare preferred since they can be handled most readily.

The following compositions illustrate the adhesive compositions of thisinvention. Unless otherwise indicated, all parts and percentages are byweight.

Composition A Parts Composition B Nacrylic 25 4445 (An acrylate polymeremulsion of about 92 parts butylacrylate, 8 parts of acrylonitrile andabout 2 pans, based on the combined weight of the acrylate andacrylonitrile ofN-methylol acrylamide commercially available fromNational Starch and Chemical Corporation-45% solids) 90.0 Copolymeremulsion of 70 parts methacrylic acid and 30 parts of ethyl acrylate-20%solids 4.0 Colloids 585 (A defoamer available from Colloids of Carolina,High Point, North Carolina) 0.1 Ammonium chloride catalyst 0.25 WicaThica 6038 5.0

Composition C Nacrylic 25-4445" 87.0 "Colloids 585" 0.1 Ammoniumchloride 0.5 Emulsion polymer of 10 parts acrylic acid, l0 partsethoxyethyl acrylate, parts ethyl acrylate and 2 parts. based on thecombined weight of the acrylic acid and the acrylates, of N-methylolacrylamide-307r solids 1.0 Acrysol ASE-60 (A cross-linked acryliccopolymer emulsion available from Rohm and Haas Co.) 5.0 Ammonia 1.0

Composition D "Nacrylic 25-4445 100.0 Copolymer emulsion ofa mixture ofabout 22.5 parts acrylic acid, 108 parts ethyl acrylate, I2 partsdibutyl maleate, 7.5 parts methacrylic acid and 3.6 parts of N-mcthylolacryIamide-207o solids 15.0 "Colloids 585" (ll Ammonium chloride 0.5Wica Thica 6038" 5.0

Composition E "Nacrylic 25-4445 lO0.0 Colloids 58S 0.2 Copolymcremulsion of 78 parts ethyl acrylate, 5 parts methucrylic acid, 15 partsacrylic acid and 2 parts, based on the combined weight of the acid andacrylate of N- methylol acrylamidc-ZOV: solids l5.0 Ammonium chloride0.25 "Wica Thica 6038" 80 Films of the above-described adhesivecompositions exhibit improved tensile strength, elongation, cold flexcharacteristics and resistance to organic solvents.

The effect of organic solvents on films of the adhesive compositions wasdetermined by immersing thin films cut 1.5- inches square inperchloroethylene for 2 hours and thereafter measuring the change inarea to compute percent area increase. A film from composition Eexhibited a percent area increase of only 187 percent and demonstratedexcellent cold flex at 0 F. When a film similar to that obtained formcomposition E is prepared except that the acrylic acid copolymer isomitted from the composition, the film exhibits a percent area increaseof 314 percent. The above test demonstrates the improved solventresistance of the adhesive compositions of this invention comprising acombination of the acrylic polymer and an acid polymer.

The improved tensile strength exhibited by the films prepared from theadhesive compositions of this invention as compared to films obtainedfrom the acrylic polymer itself, is demonstrated by preparing thin films4.5 inches by [.5 inches which have been cured for 3 minutes at 300 F.The tensile strength is determined in accordance with the standard GrabTensile Test (A.S.T.M. d1682-64) utilizing a crosshead speed of 12inches/minute and a chart speed of5 inches/minute. The breaking load andpercent elongation at break are recorded.

Films prepared from composition E are found to have a tensile strengthof 2.03 pounds and a percent elongation of 730 percent whereas filmsfrom a similar composition except that the acrylic acid copolymer isomitted were found to have a tensile strength of only 0.67 pounds and anelongation of 695 percent.

The adhesive compositions of this invention have been found to beparticularly useful in textile applications such as in the preparationof laminated fabrics, flocked pile fabrics, etc. Such fabrics have beenfound to exhibit improved flexibility and drape at low temperatures. Theflocked pile fabrics may be made into such products as wearing apparel,blankets, towels, upholstery material and rugs. These products exhibit aresistance to abrasion and organic solvents which increases thecommercial acceptance of such products.

The utility of the adhesives in the preparation of flocked pile fabricswill be described to illustrate one of the useful applications of theadhesive compositions. Processes for preparing flocked pile fabrics arewell-known in the art and need not be described in detail in thisapplication. Briefly, a substrate or backing material is provided, andthis material which may be any.material conventionally employed inflocking operations such as for instance, jute, cotton, paper, rubbersheeting, plastics, woven fabrics, knitted fabrics and nonwoven fabricsincluding felts of natural and synthetic fibers and filaments, is coatedon at least one side with the adhesive. The adhesive may be applied inthe formof a continuous film or printed on selected areas of thesubstrate. A plurality of flock fibers are then distributed onto theadhesive layer and oriented in such position that one end portion ofeach of said fibers is em bedded in the adhesive layer. The nature ofthe orientation of the fibers is dependent upon the type of flockedfiber distribution means employed and these include sprayingormechanical or electrostatic methods. The mechanical and electrostaticmethods of fiber distribution and orientation provide a more uniformorientation of the flocked fibers in an upstanding position thanobtained by the spraying method. The most unifon'n orientation of theflocked fibers perhaps is acquired through a combination of themechanical and electrostatic methods wherein a relatively highpercentage of the fibers assume a position substantially normal to theplane of the substrate with their end portion embedded in the adhesivelayer.

Any type of fiber which is normally employed in flocking operations,either natural or synthetic, may be utilized, but best results areacquired through the use of fibers in a ranged from dust to 60 denierwith an overall length of up to about 100 mils or more depending upontheend use of the product. For example, longer fibers may be desirable whenthe end product is to be a towel or a carpet whereas shorter fibers maybe preferred where the fabric is to be utilized in the preparation ofwearing apparel.

The amount of adhesive applied to the substrate likewise is not criticaland is determinedby the anticipated end use and the properties desiredtherein. An adhesive thickness of up to about to mils dry has been foundacceptable. The adhesive may be applied to the substrate as an aqueousemulsion or in an organic solvent either in one application or in twoseparate applications. in the two application procedure, the firstcoating is applied as a more viscous mixture in order to provide acoating with a minimum of strike-through. This is followed by a secondcoating to which the fibers adhere and which may be of a lower viscositysince strike-through should not present a problem.

Once the fibers have been embedded and oriented into the adhesivecoating, the adhesive is cured or set to fix .the fibers therein. Curingis accomplished by heating the fiber-impregnated, adhesive-coatedsubstrate. The temperature of the curing will depend upon the particularadhesive utilized and, also, on the desired rate of curing. For example,when the flocked fabric is prepared in a continuous apparatus, shortercuring times are desirable and higher temperatures areutilized in heatedovens.

The following example will illustrate a procedure for preparing flockedpile fabric of the type contemplated by this invention. In this example,the substrate is a high wet modulus rayon sateen fabric, the adhesivecomposition is composition E described previously and the flocked fibersare rayon fibers of 5.5 denier comprisinga mixtureof fibers of from 60to 80 mils in length. The sateen is first coated with a base coat ofcomposition E with the viscosity adjusted to about @5000 c.p.s. (asdetermined on a Brookfieldi Viscometer using a N o 6 spindle at a speedof 4 r.p.m.) to a pickup of approximately l.5-ounces per yard of sateen,dried and, thereafter top coated with the e composition to a pickup at3.5-ounces per yard. The total dry thickness of adhesive isapproximately 9 mils. The flocked fibers are then deposited using acombination of a heater bar and electrostatic techniques. The flockedfabrics prepared in this manner then are dried by heating to atemperature of 280 F. for 2 minutes and thereafter cured in a forced airoven at a temperature of 300 F. for 8 minutes. The fabric is then dyedchoosing a direct dye, and the fabric is in contact with the dyesolution maintained at a temperature of about 200 F. for 1 hour. Afterrinsing and drying, the fabric is ready for conversion to the desiredend product.

Fabrics prepared in accordance with the above procedure were evaluatedtodetermine their abrasion resistance, cold flex properties, washabilityand dry cleanability. The cold flex characteristics of the flockedsamples are demonstrated by placing the samples in a freezer compartmentwherein the temperature is maintained at.0 F. The samples are left inthe freezer for 15 minutes to insure that the freezing is complete. Thesample then is handled while still in the freezer to determine its hand,draped over some solid object to determine its drapeability, flexed,rubbed, shaken for rattle and compared with other samples. Fabricsprepared in accordance with the above procedure utilizing composition Eas an adhesive exhibited good cold flex properties.

The abrasion resistance of the above prepared flocked fabric isdetermined utilizing a Taber Abrader fitted with CS l0wheels, 500 gm.weights and run for 1,500 cycles. Samples tested in thismanner showed nosignificant loss of flock and no substrate could be viewed through theflocked fibers indicating excellentabrasion resistance of thefiockedfabric.

The dry cleanability of the flocked fabric is determined by subjectingthe fabric to 5 washing cycles in perchloroethylene each lastingapproximately 30 minutes. This test used is AATCC TestMethod 1963 T,Durability of Applied Designs and Finishes. The fabrics which have beensubjected to five dry cleaning cycles showed very little loss of flockand retained their excellent cold temperature flex properties. Theabrasion resistance of the dry cleaned fabric also was tested and foundto be good.

The machine washability of these flocked fabrics is determined bysubjecting the fabrics to 5 cycles in an automatic washing machine (withtumble drying between cycles) at l20 F. utilizing a commercialdetergent. The durability of the flockedfabrics was found to beexcellent.

Similar results are obtained when other substrates and other flockedfibers are utilized in the preparation of flocked pile fabrics. Forexample, nylon flocked fibers having about the same denier and length asthe rayon fibers described above provide an excellent flocked fabric.

That which is claimed is:

ll. A flocked pile fabric having improved cold flex characteristics andsolvent resistance comprising a. a substrate,

b. an adhesive layer on at least one side of said substrate, saidadhesive layer comprisinga composition comprising from about to99 partsof a water-insoluble, self-crosslinking acrylic polymer, an air-driedfilm of which has a torsional modulus of 300 kg/cm. at a temperature ofless than about -40 C. and from about 1 to 20 parts of an acid polymercomprising a major amount of an acid ester and minor amounts of anacrylic acid, and

c. a plurality of fibers, each having one end portion em bedded in saidadhesive layer.

2. The flocked pile fabric of claim ll wherein the acrylic polymer ofthe adhesive composition comprises from about to parts of an acrylicester, from 2 to 15 parts of acrylonitrile and from 0.5 to 5 parts of amethylol acrylamide.

3. The flocked pile fabric of claim 2 wherein the acrylamide inN-methylol acrylamide and the acrylic ester is butyl acrylate.

4. The flocked pile fabric of claim 1 wherein the acid polymer comprisesfrom about 60 to 85 parts of an acrylic ester, from about to 30 parts ofan acrylic acid and from about 0.5 to 5 parts of a methylol acrylamide.

5. The flocked pile fabric of claim 4 wherein the acrylic acid is amixture of acrylic acid and methacrylic acid.

2. The flocked pile fabric of claim 1 wherein the acrylic polymer of theadhesive composition comprises from about 85 to 95 parts of an acrylicester, from 2 to 15 parts of acrylonitrile and from 0.5 to 5 parts of amethylol acrylamide.
 3. The flocked pile fabric of claim 2 wherein theacrylamide in N-methylol acrylamide and the acrylic ester is butylacrylate.
 4. The flocked pile fabric of claim 1 wherein the acid polymercomprises from about 60 to 85 parts of an acrylic ester, from about 5 to30 parts of an acrylic acid and from about 0.5 to 5 parts of a methylolacrylamide.
 5. The flocked pile fabric of claim 4 wherein the acrylicacid is a mixture of acrylic acid and methacrylic acid.